The present invention pertains to cored wires for treating molten metals to remove unwanted impurities and in particular to the manufacture of cored wires having a reactive metal core.
Cored wires, in particular a calcium core surrounded by a sheath has found wide application in the treating of molten ferrous metals. The cored wire is used to introduce calcium into the molten ferrous metal, after being tapped from a furnace, in order to reduce unwanted elements such as sulfur and oxygen in the molten bath. A detailed discussion of the overall process is contained in U.S. Pat. No. 4,481,032, the specification of which is incorporated herein by reference.
U.S. Pat. Nos. 4,512,800, 4,705,261, 4,094,666, 4,698,095, 4,035,892, 4,097,268, and 4,671,820 all disclosed various methods of treating molten metals using a clad reactive cored metal composite in the form of an enlongated wire.
In one method of manufacture, a calcium metal core is extruded into an elongated shape or wire which has a generally circular cross section. The core wire is inserted into a metallic sheath, e.g. steel, as it is continuously roll formed into a tube. The tube is formed with a mechanical lock seam so that reactive metal, e.g. calcium, is encapsulated or locked inside. The resulting structure or product is a continuous tube or wire being a composite of a reactive core and a roll formed metallic sheath. One of the problems with the prior art roll forming process is insertion of the core into the metallic sheath.
Another problem with the prior art process has been monitoring the roll forming process to identify a problem with the lock seam at the earliest possible stage of the process in order to prevent excessive amounts of malformed lock seams and thus scrap cored wire.